Telephone system.



F. MHSLOUGHL TELEPHONE SYSTEM. APPLICATION FILED JAN. 19, I915.

Patented Mal. 25,1919.

3 swans-sum. 1.

1N VEN TOR.

Patented Mar." 25,1919.

R m I E wwwhmwlww M mw OQ MW jL/QTAT UNITED -fsirafrns PATENT "curios.

ream: M. SLOUGH, or ELYRIA, ,o'HIo, AssIGNoR, BY MESNE AssIGNivrENrs; '10 -STROMBERG-CARLSONTELEPHONE MEG. 00., or ROCHESTER, new YORK, A

'oonrom'rron ornnw OR all whom it may concern:

Be it .known that I, FRAXK M. SLOUGH,.

a citizen of the United States, residing at Elyria, in the county ofLorainand State 5 of Ohio, have invented certain new ,and useful Improvements in Telephone Systems;

and'I. do hereby declare the following to .be a full, clear. and exact description of the invention, such as will enable other skilled .0 in the art to which is appertains to make and use the same. w

' My invention relates to telephone systems; and the objectof the same is to make certain improvements in telephone systems.

5 In the. telephone systems now. in use, the

substations are provided withsignals and means are provided at the main station for causing'the actuation of said signals; There is also provided a substation mechanism through which the operator controls the f actuation of such signals.

One of the objectsof myv invention is to provide a system in which but a single set w of controlling. mechanism is employed at- 25. each operators position. lVith ,this object in yiew, I have provided at each position a single controlling mechanism for controlling the actuation of all of the signals of'the particular ch-aracter in the system. I have also, with this object in view,' prov1ded.

I operated without the operation of the con- 40'trolling mechanism, the operation of the switching mechanism atthe'main station of the system being sufficient to place the signal actuating means in a position to cause the actuation of the substation signal, and at the am'e. time, I associate the-apparatus for a manner which will be described. I

I also aim toprovide a system which ,will

reduce the time necessary to make a connec tion, and in which work hitherto done by the operator is done 1;. the electrical and me chanical apparatus in the system. In other words, I aim to-speed up the worksoas tov reduCe the-nu'mber of operators required.

Specification .of Letters Patent.

tem' embodying my invention- 1 rugs and first omplishing both of these objects together,

TELEPII-QQQIINE SYSTEM.

Patented Mar. 1919'.

Application filed June 19, 1915. Serial 1%. 35,013.

Another object of my invention is to proe v de a system 1n which a plurality of sys: tems of selective-signaling are superposed matic ringing for the telephone system.

Another object of my invention is to pro- .vide means to prevent the application of the signaling current during a ringing period. For; example, suppose the signal "of the party desired to'be arousedwas three short rings, and the apparatus was cut-in afterthe code determining mechanism had.

passed one of these'short' rings, then the first signal would be two short rings, which would be false and callthe wrong party. I provide 'means'whereby it is'impossible to cut in on thesignalingexcept before the beginning of a ringingperiod;

Another object of my nvention is to com-. me suchneans with apparatus realizing otherobJects which I havefset forth above.

-Other objects of, my invention and the invention itself will be better understood from a description of embodiments of the same.

Figure 1 is a diagram of a'system em-. bodyi'ng my'invention.

Fig. 2 is a second diagram of a second system embodying my invention. I a Fig. 3 is athird diagram of'a third sys- Referring now to the draw to Fig. 1, in which there is illustrated a common battery telephone system embody- ;,'-ing my invention, at A and E are shown telephone lines. The telephone line A, hereinaft-er spoken ofas the calling line, leads from a substation shown at B to a mam or .central statlon, shown at C. But one substation is shown on the line-A, though.

any suitable number may be connected to this line. The line E, which will hereinafter be spoken of as the called line, leads from a .plurality'of substations F, F F and F to the main station -0.. Four substations have been shown upon the line E, though any suitable number may be connected thereto. The talking apparatus at the substation F has been'illust-rated. at F, the talking ap-- Y paratus' at the other substationshaving been omitted from the drawing for convenience, ,it beingyvll understood from the apparatus .and whose operations are determined by a.

system of keys orsw1tches. I also aim'toi do this. and at the same time provide auto- I shown at F that talking apparatus is con-- D to telephone lines. here shown as switchmg means G andI-I: The switching means G, hereinafter spoken of as the answering switch, in the form shown comprises a plug P, hereinafter spoken of as the answering plug and a jack J. The switching means H, hereinafter spoken ofas the calling switch,

in the form shown comprises a plug P hereinafter spoken of as the calling plug and a jack J The jack J, as well as a second or. multiple jack J, are at the main station and connected to the telephone line A. The jacks J, and J 2 are likewise at the main station and are connected to the line E. The central station operators "set is shown at K. actuating the substation signals are shown at M, M M and M Controlling means for the substation signaling is here shown at Z, Z and Z b When the hook-switch at the station B is operated, the line lamp 4 will be actuated in.

the usualmanner, and the operator, observing its actuation, will operate the switch G by inserting the plug P into the jack J. The relays U, V and X will be operated, the relay U closing a circ'uitthrough therelay O, which will be actuated, connecting the op- ,erators set K to the cord. The relay 0 also connects the keys Z, Z and Z to the rclays S andT. The operatorhaving learned the station desired, will proceed to signal the subscriber thereat. t

In the embodiment shown, the operations for setting up the signaling arrangement a will be different with respect to each of the four stations upon the'lf called line. For the character of signal shown at F,, which may be a harmonic ringer of a certain frequency, or any ringer responslve to any frequency,

-.tl1e operation will be as follows: The operator simply. closes the switch H by inserting the plug. P into the jack J,,'which will cause the actuation of the relay U The relayU will short-circuit the relay 0 and complete a circuit for the relay Q. The

. relay 0 being a slowacting relay will maintain thecircuitof the relay Q long enough for the relay Q to be energized, and to'complete an. alternate or looking circuit for itself. Thev relay Q completes the ringingconnections from the device M and the operation of the signal at F, takes place.

When the subscriber F responds, the relay R is actuated and the source M disconnected, the parts beingrestoredto the condition shown in the drawin The sources of' current for the hook-switch 7, which closes a switch 8 Ifillt is desired tooperatethebell atv F,

relay T, which'immediately pulls up, looking itself and disconnectingthe key from itself. and from the apparatus associated with the cord D. A circuit will also be completed for the relayQ, which contains contacts of the relay T. The operation will be the same as previously described, the current now flowing from the source M.

When the station .at F, is desired, the key Z is operated, causing the energization of the relay S instead of T, otherwise, the operation will be the same as previously described. When it is desired to. operate the bell at F. the keyrz, is operated, causing the energization of both relays S andiT. These relays will, operating in substantially the same manner as previously described, connect the source M to the called line. After the ringing andthe response of the tions, the circuits of the relayV and V will 1 be broken, completing a circuit for the relay R which disconnects the switching" device G from the cord circuit. At the same time, the lamp 5 is operated, signaling the operator, who withdraws the'plugs'from the jacks,

and the system is restored to normal.

More specifically, the operation of the system is as follows: The operator at B initiates a call by removing the receiver'6 from in the circuit of the relay lV, which will be operated from ground at 9battery 10 VV-switch ll-conductor 12-.switch 8- transmitter 136conductor 14switch l5-to ground at'16. The magnet W will close a switch 19, completing a circuit through the lamp 4, as follows: 910- 19-{1-16. The lamp 4 is so located that its actuation can be observed by the opera tor at the station 0, wl1o controls the cord vcircuit D. The. switch Gris thenopetated y I the operator by the insertiontof' the plug P into the jack J ,fthe contacts 20, 21 and 22 of the plug registering respectively with thecontacts 23, 24 and 25 ofthe jack. At the time the lamp 4 was actuated a lamp 4,

was also actuated, associated with the jack.

J at another position. The operation of the. switchingdevlce G' completed one circuit through therelays X and U and another circuit through the relay V. The first cir cuit is as follows':' l6-X-23-22'" switch 26"conductor' 27-conductor 28- device 29 --T, -.---battery 30 00 ground ,"31.

The magnet X opens the switches 11 and 12 15, interrupting the circuit of the-magnet W, WlllCh opens 'the'circuit of the lamps 4 and 4 The magnet U closes 'a switch-32,

. completing a shunt 0f the device 29. The ob ect of this-'11s to prevent the operator at u another position answering the call, as with the device 29shunted in the cord- D another operator with the device 29 incircuitwith her magnet, corresponding to the magnet U,

would not get sufiicient current to operate' her magnet The magnet U al'so closesa switch"33 in the circuit of the relay and a switch. 34, for a purpose to be described. The circuit of the relay ,V includes the battery 35, the

talking strands 36 and 37 of the cord, the

contacts of the plug'and jack, the limb of the line A and the substation apparatus thereon. This relay opens a switch '38 in the circuit of therelay R preventing the operation of that relayduring the ringing and talking. -The relay V also closes a switch 39, for a purpose to be described. The relay Qwilllnow be energized over the following clrquitz 3180 lamp -i0switch 33 conductor 48-switch 44ground 45. Thefiow of current through this circuit will be :suflicient to operate the magnet 0, but 'insutfi cient to operate the lamp The relay 0 closes the switches 46 and 47, connecting the operators set 'K through the conductors .48 and 49 with thecord circuit, placing her in communication with the subscriber at B p over the conductors 48 and 4,9-the strands-v of the cord circuit 86'37the contacts of the switching device G'the line limbs 12 and 14: and the substation set at B, current being furnished fromjthe-battery to both ends of the cord cir'cuit,in the usual-manner, through the relays V and V -VVhen the relay 0 was energized, it closed the switches 50, 51 and 52 and opened the switch 53-al1 for purposes which -will appear from a further description.

Assuming first that it is the subscriber at F that is desired, after testing the line in the usual manner, the test circuit being shown at 54 including a switch '55, and after finding the line idle, which is the-'casehere assumed, the plug 1? is inserted into the j ack J completing a circuit through therelay U as follows: ground 56-battery 5'7.U conductor 58-switch ground 59. U closes a-switch 60in the circuit of the rel'aj- Q, a switch 61in a shunt of the relay 0, and opens the switch 5'5, breaking the test circuit and closing switches (SQ-and 63, for purposes to be described. The closing of th'eswitch 61 com-;

pleted a shunt 64E of therelay O. causing the deenergization of the 'same. The relay ,0, when deenergized, opens switches in the circuit of the operator's telephone set 1x, disconnecting the samefrom the cord circuit, and also opens switchesand 51 in the circuit leading to the switching devices Z, Ziand Z thus disconnectingthem from the particular cord circuit. and enabling these switches to. be used in. connection with any other cord circuit of the operators position. In this way'I am enabled to use but one set 'ofkeys for a given operators position. 0, however, being slow'actingfthe switch '61 will be closed before theswitc-h is opened,- so that for a short interval of time, thefollowing circuit will lie-completed through the relay Q 5657 .--64'.0011(l116t011 65- 62- -ground 68. The relay Q will close a switch 69, completing a. locking circuit for tor 82'switchj75battery- 83to ground at I 84. The bell at F will be operated, and as soon as the subscriber responds, the comple,

tion of the talking set bridge at the substat1on will cause the character of current flowing through the circuit to be such as to cause Relay Q the actuation ofj the relay R, which will close the switch 86, eoinpleting'afshunt 87 about the magnet Q, which will become de-' energized, restorijngthe' ringing apparatus 'to the condition-illustrated in the drawing.

. At the time the called. subscriber re? sponded, the relay V would also be actuflated over a circuit verysimilar to that described in connection with the relay l, ex-

cept that the, limbs of the called line and the calling end of-the' cord are included therein. \Vith the apparatus in this con dition the conversationtakes place, and at the termination of the conversation, the circuits of the relays" V and V, will be inter rupted when the receivers at the'substations are. restored; A'circuit. will be completed through, the relay R, as follows: 3 l' -i}()- 9OR and the lamp 5 in multiple switch 38conductor 9l'-switch 63to ground 68. The relay R, will disconnect the plug'l from the cord in a well known manner, and the {lCtHRi/IOII of the lamp 5 shows the op erator that the conversation-is terminated, whereupon she withdraws the plugs from thejacks andthe systemuvillbe restored to normal.

Assuming that the the switch H is closed, the operator throws .the key Z, whereupon the operation will be I as follows: The relay T will be operated over a circuit as fo1l0wsground 9-1-ZCODdll tor 95-5196- switch 97relay T- battery 98' to ground '99. The relay will be eneroperator learns that it' is, the subscriber at F that is desired before gized, first closing a switch 100 and com tlet ing a circuit for itself independent of. the.

key Z, as follows :99 98T- 100"conductor 87-conductor 101'conductor 102-34 -39 --103 to ground. The generator M will, be disconnected from the conductor 79 bytlie openingof the switch 7 8 and the generator M will be connected to such conductor 1 by the closing'of the switch 105, both taking "place whenthe relay T is operated.

The. operator now operates the switch H,

1 whichv completes a circuit for the relay U 'tionof the system will be the same as pre- Viously described in connection with the signaling of the substation at F Assuming that it isthe substation at F,

that is desired, the operatorupon learning thisfact, actuates the key Z which completes acircuit'thrQugh the relay S, as fol lows: 94-Z,10750108-switch l09 -S...9 8 and 99'. The relay S being energized, closesa switch 110 and completesa Y locking circuit-for itself independent of the .101- -'102-to ground through the switch,

35. f w ith 'the relay T. Immediatelyafter the closingof the switch 110, the switch 109 is 103,: as previously described in connection opened, releasing the key Z for use in connection'with other cords. The operator then closes the switch H, whereupon. the relay Q,

-is energized over a circuit similar to that described in connection with the operation of "the key Z, except lOIlOW lncludes the device S and the switch 110 instead of the relay T and. the switch 100. The relaySwill open a "switch 77 and close a switch 120, connecting [the generator M to the called line.

The

- Subsequent operations of the system will be 'the same as "previously described.

Assumingthat it is the subscriber at F that IS desired, theoperator upon 'learnlng that fact, depresses the key Z completing circuits for both the relays S and T, as previously described. These relays ,operate, performing the functions previously described, the generator M now being connected through the lead 121, the switches 122' and 105 to the conductor 79. Upon the operation of theswitchingdevice H, the source 60 M -will be connected to the called line throughthe-operations and connections pre- Viously referred to in describing theconnection ofthe generators M and'M to. such el The subsequent steps in the operation w ll'be thesame as previously described. I"

I will now refer to the embodimentof my invention illustrated in Fig. 2. In addition to accomplishing the objects accomplished by the system shown in Fig. 1, the system in Fig. 2 enables me to control the operation of a large number of signals on a telephone line, at the same time realizing all of the ad rant-ages set forth in the system shown in Fig. 1. In so far as I have used letters for references in Fig. 1, duplicate parts have been'referenced in Fig. 2 by the use of the same letters, except instead of using capital letters, as in Fig. 1, I have used small letters in Fig. 2. Except for the signaling of the sub-stations on the called line, the operation of the system shown in Fig. 2 is so much like that shown in Fig. 1 that I will not repeat that'part of the description of the apparatus, limiting myself to the description of the signaling.

There is added in Fig. 2 a pair of commutators A and A whichinay be connected by a shaft A so as to rotate in synchronism.

, \Vhen the ringing is controllcd by the commutator A the ringing period will be continuous; that is, there will be recurring, con tinuous applications of the ringing current. When the ringing is controlled by the com.-

mutator A these recurring periods of ringing will be broken up into impulses. Perhaps this will be-better understood if reference is made to the old code system of ringing. The commutator A determines that the ringing shall be according to one signal of the code signaling, say one short ring. and that dcterminedby A will be according to adifi'erent. signal in this cord, say two short rings, these rings it being understood,

occurring at intervals, according to the-relative slze of the segments of the commutator.

There have also been. added two relays A and A The relay A 4 controls the limb of the line to whichthe ringing current is .applied and the relay A determines which of the commutators A, or A, shall control the character of-the ringing. An additional relay a has been supplied for purposes'which will be understood in the description of the ope-ration.

For the purpose of illustrating the similarity between the systems shown in Figs. 1

and 2 and giving the reader the clue,I will describe the operation whcnstraight line ringing is to be effected. For this purpose we will assume that an additional substation is bridged across the line 6, as is done on the 169. Ah the same time, the relay g will shunt'the relay; through the shunt 170 and If the relay 0 willshowly release the switch 164.

i described.

in thecircuit of the relay Q, which has been During this interval of time, the

relay Q will be actuated, completing a lock- .ing circuit for itself, as follows: 156+157.-

1 T ay 9 will be energized, compl mg the ringingcircuit. as follows;

ground atl74.-ringing generator wi -switch:

. '175' switch 176--now closed contact 177- '178-a-conductor 17 9switch 180'con-- ductor 18l'switch 182to the contact 183" of the plug out over the limb 185 of' the called lineethrough the substation' bridge,

back over the other limb 184-through .the

i plug 77 to the contact 186..conductor 187- switch .188-conductor 189 -switch 190' -to .ground at 204..

ground at 191. This circuit will be openedand closed at 177 by the relay a over a circuit, as follows: 156157- -now closed switch 200-conductor 201 relay a switch It will be seenthat if the relay A were actuated the commutator A, would control the ringing period's through the relay a. Suppose that it was the subscriber at station 7 that was'desired. The operator depresses ground 205'z conductor 2061 now closed "switch 207conductor 208 rela'y A -to ground 191.- RelayA' would be energized, 'breaking the circuit just described'at 209 .55. I "is designed to produce a special kind of the key a, completing a circuit, as follows:

and releasing the key a, as previously described; The relay A would also close a. I .switch 210, completing a locking circuit for itself, as follows: 191'-A 210 -conduc f code signals.

tor l62-- switch 212conductor 21 3now closed switch 21 .-to' ground at 215. The

rela y'A will open the switch 202, discon-' necting the commutator A and close a switch 220, connecting the commutator A,

I into the circuit of-the relay a. When the switch h has operated, the relay. a will be operated at intervals, determined .by the character 'of the segment A, which in the I embodiment illustrated in Fig. 72' will at 111- terwals place-two short rings upon the line. The relay 9 having also been energized. com-' pletes the ringing circuit. which in this case w ll be as" follows: 174m -175-176 171-178 'r 179 180 -18l182183 185-signal fto ground 2'21 and through ground [back to 174. The generator 771 current. say current of a certain frequency to which respond only signals tuned to that freouency. The bell at f is tuned to respond to the. frequency of current generatedby the- The bell at f is also tunedto respond to this-frequency,'but the slgnal ngenerator 122...

tended for the station f is one ring only,

such as is determined by thecommutator A andin fact, if the switch h was closedwlth generator will be'connected with the side lS-i to-the frequency of the current produced byeither of the commutators, so that currents of any of the frequencies producible by necting the generator m, to the side 185 of this frequency, but the signal intended V the-station is tworings instead of one. If

out the operation of any of the keys, current would pass over the same ringing circuit as has been'described, the commutator A now determining the periods of ringing.- I Assuming that it is the subscriber at f that is desired, the key 2 will bedepressed, completing a circuit through the relay A4; The ringing circuit will be the same as described in'connection with f except that the 75 of the called line by the opening of vthe switch 190 and the closing of the switch 222 The circuit will t-hen'be as follows: 174-.- 77?, '1751 T61771787 -222189+ 188.186-18lthrough f -to ground at 80 223; The signal for 72 is one short ring,

-'determined by the-character of' current produced by the generator m The sig nal of the subscriber. at f will be two short rings of the same kind of current. The operation of the key .2, will cause the signaling of the subscriber at f as it will'be seen that the operation of this key will complete the circuits of both the relays A; and A A connecting the ringing to the side 184 'of thecalled line and the relay A cutting out the commutator A and connecting in the'commutator A There are thus on each side ofthe line' a two bells which respond eadh' of the generators. Each generator is adapted too-be connected to either side of theline and each generator-is adaptedto be con-, nected to either side of the line through plished by the operati'on'of the-key e On the sidel84r the signal at f, responds to the frequency of current produced by the generator m and the subscriber at f responds to a signal of one ring. This signal is operated by connecting the generator m to the side 184.- of the called line when the commutator A controls the ringing circuit. This is accompl shed by operating the-relays t and A The key 2 controls the circuit of these relays and its operation will. cause th operation of the bell at f,. 12 5 The bellat f responds to the same curirent, but the subscriber at f, knows that h s signal is two rings instead of one. f is,"

therefore, signaled when all threeof the relays t A and A are operated. This is .0- 0

eomplished by the actuation of the key 2 The bells at f f 7' and 7' respond to the frequency of current produced by the gene'- rator m The subscribe-rs atf and f know that their signal is one ring, which is de- --termined by A; and t-he'subscribers at f andy", know that their signal is two rings of the character produced by A To ring 7", the generator m must be connected to the. side 1850f the called line with theconunutator A controlling the character of current; This is accomplished by the op-' eration' of the relay 8 through the key 2 The operation of 2,, completes a circuit through the relay 8, which connects the gena crater 122 through the switch 2% into the circuit previously described, including the limb 185. i f v To signal the subscriber at f it is necessary to complete the same circuit,except to shift the commutator by the actuation of the relay A,,. This is accomplished through the a gcncy of the key 2 which controls the circuits of the relays s and A To signal f .the relayss and A, must be operated, the

relay 8 to connect'the generator m, in the ringing circuitand the relay A, to connect the ringing circuit to the side 184. This is controlled through the agency of the key 2 which completes the circuits of the relays t and S simultaneously. a a I To cause the signaling of the subscriber at I' -the relays s, A, and A, must be actuated,

the relays to connect thegenerator m, in the ringing circuit, the relay A,,to connect the ringing generator to the side 184; of the called line and the relay A to shift the controlfrom the commutator A, to the commutator A This is accomplished through the agency of the key 2 A fourth generator m is provided which furnishes current of a frequency calculated to operate the signalsat f f f and f To call the subscriber at i it is necessary to connect the generator m, in the ringing circuit without any other changes, since the signal of the subscriber at. f,,, is one ring. This is accomplished by the operation of the relays s and 2., which are controlled by the actuation of the key at 2, However, to sig nal the subscriber at 7, whose signal is two rings, the commutator A, must be connected 1n, and to do this, the relay A, must be actuated. This is accomplished through the agency of the key .2 To signal f whose signal is one ring, the relays s, tand A,

must be ope-rated, s and [to connect the generator m, to the ringing circuit and A to connect the generator to the side 184 of the called 1ine.- This is accomplished by the operation of the key 2 The subscribe-1' a f1 6',

' whose signal is two rings is called by the op-- eration of all four -f the relays, the relays s-and tto connect m to the ringing circuit,

the relay A to connect m to the side 184 of the line andthe relay A}, to shift the control from the commutator A to the commutator A,. This is vaccomplished by the operation of the key 2 .It will be seen that in each case, immediately after the actuation of the key, the

same will be released for use in connection with other cord circuits, and that I am en abled to accomplish this in connection with automatic ringing for the signaling of subscribers upon lilies on which the signaling is detei' inined according to two difierent systems-"of selective ringing.

I will now refer to the embodiment 40f my invention illustrated in Fig. 3. The calling line is illustrated at a, themain station at c, the connecting means, here shown as-a cord circuit, at d, the called line at e,the

' connecting switches at 5 and h, the-plugs at p and p the jacks at j" and 7' Ate I illustrate a v second called line provided with a jack j, \Vhen the answering switch 5 is operated, the relays u and 0 will be operated, 0' connecting the operators set L to the calling line. The operator learns the subscriber desired, and after testing the called line, operates the switching device 7H,,assuming that it is the subscriber at f'- that is desired. lVhen h is operated, the relay 2:, will be operated, completing a circuit forthe relay q, as follows: 300 switch tor 306now closed switch 307ground 308. The switch 807 was closed when the relay u was energized and the switch 304:

wasclosed when the relay 0"was deenergized, owing to the closing of a shunt 309 about the same by the relay u Therelay will be alternately energized and deenergizethowing to the operation of the commutator A which closes a. shunt 310 about said relay. This shunt is as follows, beginning at the point 311 conductor 3l0the switch 312con-ductor 313-the commutator A to ground at 314. When this shunt is completed, the relay q will vbe deenergized and there will beno sending of ringing current to the called line. This will be spoken and assuming that one signal is' bridged It will beunderstood that the.

across the line,v as s'hownat f upon the line e-, back over the line through. the now closed switch 32lconductor 322 switch 323'to ground at 32k When the subscriber v,

responds the relayu will be operated, clos ing a circuitfor the relay 320 as follows:

3 21s\ vitch 322now' closed switch 323 conductor 309now closed switch 32-lto ground 325. The relay 320. 'will break the circuit of the relay. 9' and permanently in- .terrupt the ringing circuit. At the term1 na tion of the,co1 1versation, the relay '0 will be deenergized and the. plugs withdrawn from the jacks, restoring the; system to normal.

As mthe system .shown in Fig. 2', means vare provided for modifying the ringing A andin'; the; form shown; is calculated to periods according to-a predetermined code, .here-shown as a plurality of commutators A and A A, is differently arranged from break the ringing period up intov a p'redes terminedcharacter and numberof rings. "The commutator illustrated-at A, breaks this ringing period up intotwo short rings. As in Fig. 2, means are provided for'determining which of these commutators should be employed, hvre shown-as a relay A .Mechanism it provided for preventing the application ofthe ringing current at any intermediate point during the ringin perit'id when the conimut-ator'A, is employ d. This is done for the reason-that "the ringing current ;might come on during the ringing period determined .by this commutator when one of the segments of the. commutator has passed,-' so that it would cause but one short ring, thus resulting in-a false signal.- In the form shown,- this commutator controls a shunt of therelay g for-the same-purposes,

as the shunt already described which is controlledby the commutator A The. shuntcontrolled by A isas follows: 310 switch 340conductor 34:1 conductor 342 commutator A 'to ground at 31-4. This shunt is controlled by a relay'345 andin-the form shown, the shunt cannot be made until the relay, is energized. A circuit is provided for thisrelay controlled by the commutator in such a way that the'circuit of 345' cannot be ;made except during asilentperiod. In the form shown, this is effected by a switch. 346 in the circuit of 345, which is controlled-by thecommutator. This switch may be controlled by forminga projection 350 upon the "commutatonwhich closes a switch when it engagesthe spring 351; p I Assuming now that it is desired to call a I subscriber whoresp'onds to a signal,- the character of which is determined by the commutatcr'A the operator depressesthe keyz f,

' completing a circuit for the relay A as follows: ground 355 conductor 356 relay i A 'jto ground at 321. The relay A op- .erates,closii1g.a locking circuit for itself and completing a locking circuit for-itself- .with Fig. 2; a

that my invention is limited to such forms and details,-it being understood by those skilled in theart that departures may be- I and breakingthe circuit the key, thus releasingthe key. The relay also closes 'a switch 3l0, completing the shunt 310 about the relay 9' at the switch 360 controlled by the relav 345. This switch will be closed until the ielayis 'actuated, but. the relay cannotbe actuated until. the switch 346 is closed, which can not take place during a ringing period, sincethe protuberance 350 upon the commutator only engages the spring. 351 dining the silent period. The switch 3&6 being. thus closed during the'silent period, the circuit of the. relay 345 is closed. This circuit .is as follows: ground at -31-1- sw.itch 346conductor 365switc.h 366.relay switch 368to ground at 300; The relay 345 will be energized left-hand corner ofthesheet, illustrated in Fig.3, controls theappl-ication of a particu lar kind'or character of signaling current to the calledxline, as described in connection While I. have "illustrated theseiparticular forms andthe particular details employed in such forms, it hasbeen done for thepurpose of betterdescribing my invention, and not made from such forms and details without departing from the spirit of the intention Iclaim: I w 1. In a telephone system, the combination of a calling telephone line, substzition apparatus thereon, a calledtelephone line, a

signal on said line, a main station, link conductors at thermam statlon for connecting the telephone lmestogether, a switch ngde vice for connecting? the link conductors't-o the called line, a signaling generator at the .main station, means to connect said genera tor to said signal, ncluding sald called telephone line, a signaling key including key contacts controlling the connecting meansand mechanlsm, operable lndependentlyot said switching device and substation apparatus for relieving such key contacts from the control of said connecting means,

- 2. Ina telephon'efsystein, the combination ofa main station, a telephone line leading to the main station, a signal on said line, a

calling telephone line and substation zip: 130

' nected to and to operate the signal on the,

at F

paratus thereon, link conductors for connectin gtelephone lines together, a signaling generator at the main station adapted to be contelephone line, awi-e'layassociated with said link conductors controlling the connection of' sznd generator to said signal, and means operable independently of the substation apparatus for disassociating said key from said link conductors immediately a'tter said ciating said key from said link conductors after the generator has been connected to the signal- L. In a telephone system, the combination of a "main station, telephone line leading to the main sta tion,*a signal on the telephone line, link conductors at the main station for connectingltelephone' lines'together, a ringing generator at the main stationfor actuating the signahat the substation, "a ringing key controlling said generator normally disassocia'ted from the link conductors, means for associating said key'with said link conductors and mechanism for automatically tflisas'sociating the key from said conductors and releasing the same as soon as the signaling) operation has been started. i

5. In a. telephone system,the combination of a main station, a telephone-line leading to the main station, a signal on'the ,tele phone line, ,link conductors for connecting telephone linestogether at the main station, a ringing generator at the main station adapted to actuate the signal on the teleplion'eline, a. ringing key at the inain'station controlling the conneotionot' the generator to said signal, said key normally having no control over the connection of the generator to such signal, means at, the main station .for placing the control of the generator over said signal under said ,key and manually controlled means forautomatically releasing the key for use with other cord circuits'as soon as the ringing generator ,has been connectcdto such signal.

(i. In a telephone system. the combination" of' aringing circuit, a relay controlling the same, a circuit for said relay. a ringing key *in said circuit, nornially'open contacts in said circuit, ap 'iaratusfor closing the contacts in said circuit and placing said relay under the-control of the ringing key, a second circuit for said relay, said relay When operated opening its circuit containing the ringing key and closing said second circuit.

. T. In a telephone system, the combination ofa main statio na cord circuit at the main station for connecting telephone lines togetheig'telephone lines leading to the main station, a signal on one of said telephone lines, "a ringing generator at the main station, iaringing circuit including said generator, a portion oi the cord circuit and the called telephone 'line, a relay controlling said circuit, a circuit for said relay, a ringing key in saidcircuit, normally open con tacts in said circuit, a second relay controlling saidnormally open contactsadapted to close the same'and place the control of said relay circuit under the ringing key, and a second circuit for said first relay, said first relay when actuated opening the first named circuitand closing the second named circuit.

8.111 a telephone system, the combination of a'calling' and a called line leading from substations to a main station,-a signal on the called line,link conductors at tlicn'iain station for connecting telephone lines together, an answering and a calling switch for connectlng'the link conductors to the telephone 7 line, a ringing generator at the main station, a signaling circuit including said generator,

a portion of the link conductors and the called line,'a relay ,cont-rolling'said circuit, a circuit for the relay including contacts of a ringing key, a second relay controlling normally open contacts in said circuit, said second named relay being controlled by the answering switch, and a second circuit for said first named relay, said first named relay when operated opening its first named circuit and closing its second named circuit, thereby releasing the key for use with other cords. i i

9. In a telephone system, the combination of acalling and a calledline leading from substations to a main station, a cord circuit at the main station. for connecting said lines together, an answering switch for connecting the cord to the calling line, a calling switch for connecting the cord to the called line, a signal on the called line, a source of current at the inain station for operating said signal adapted to be connected to said signal, a ringing relay, a circuit for said ringing relay, a second relay controlling said ringing relay circuit, a circuit for said second relay, a ringing key controlling said second named circuit. a third relay controlling the circuit of said second relay, said third relay being controlled by the. answering switch of the cord circuit, a second circuit for said second relay independent of said ringing key, said second relay when actuated opening its first named and closing itssecond named circuit. 10. In a telephone system, the combination of a calling telephone line and 2. called telehone line, aQQ Zd. iii'cuitjorconn cting said calling and called lines together, a call bell en thecalled line, an answering plug and fack switch for connecting the cord to the calling line, a calling switch for connecting the cordto the called line, a ringing genera tor for ringing said bell, conductors for connectingsaid' generator to-the calling switch,

a he normally having no control over said con uctors, means including a relay controlled. by the answering switch-for assigning to said keycontrol over said conductors and means inc1uding'arelay causedzto operate at the timed-the calling switchis opi erated whenever such calling switch is, operated to establish a connection for removing v said-key fromcontrol' of the said conductors. 11. In a telephone system, the combination of telephone lines, a subscribers signal on "one of said lines, link conductors for'con- 3i? necting the lines together, an answering switch and a calling switch for connecting the link conductors to telephone lines, a source of current for supplying current to operate said signal, conductors to connect 25 said source to the line to which. said signal is connected, a key switch common to a plu 'rality of link conductors normally having too-control over said conductors, wires normally'connected to said keys; and leading to en. a plurality, of other link conductors, means controlled by the answering switch for assigning to said key control over said conduc-,

mg current to operate the signal onthe called line, means for connecting said source to said switch and the called line and said as signal, a key common to a pluralit ypoi cords adapted after said switch has been operated to control the connection of said source to said switch and mechanism controlled by said key for removing the control of the so connection of said source to'said'switch from said key as soon as said source has been con- .nectedto said switch. 13. In atelephone system, the combination of a signaling circuit, a plurality of *5 sources of current, each adapted to befconnected in said circuit, one normally connected in said circuit, a relay controlling the connection ofeach of said sources in said circuit, another source of signaling current an adapted 'to be connected in said circuit, all of said relays jointly controlling the connec-- tion of said last named source In-Said cir suit and. means controlling said relays.

ii. In atelephone systenn the combinasources of current, each adapted to be connected in saidcircuit, one normally connected 1n sa1d,c1rcu1t,'a relay controlling the connection.of'eaclrot said sources in' said circuit, a key controllin each of'said-relays, a tlnrdsource of signaling current adapted to be connected in said circuit,-,n 1eans includ- H mg alloi said relays controllingtlie" connectron of a third source, in said circuit and another ringing key controlling all of said relays; 1

15. In a telephone system, the combination of a. signaling circuit, a normally open switch in said circuit, a source of signaling current, circuit conductors included in said'so" circuit to connect said source to the contacts of said 'switch, a relay controlling said conductors and means controlled by said switch to .remove the control of said conducto rs from said relay as soon as said ring- 35 mg clrcuit is completed.

'16. In a telephone system, the combinaf tion of a plurality of cord circuits, a ring-- ing circuit, a key provided with a contact common to a plurality of cord circuits, said key controlling said ringing circuit, wires normally connected to said key and leading to a pluralityofcord circuits, and a relay having contacts in the, ringing circuit for dISHS SOCIatIDg SEIId key from a cord circuit. 95.

17. In a telephone system, the'combination of a signaling circuit including a 'plurahty of s1gnals,.a plurality of sources of signaling current for selectively operating said-signals, mechanism for selecting an'd connecting said' sources in'said circu t, a

plurality of devices for modifying-the effect of the current from said sources on said signals and means for; selectively causing said devices, each independently of the 105,

other, to modify the eiiect of the current from each source upon said signals. l '18. In a telephone system, the combination of a signaling circuit including a plu- I ralityof signals, each signal constructed to respond-to a particular one of a-plurality of currents of differentcharacter, means for "producing a number of currents of difierent character, means for determining which character of current shall be connected insaid circuit and mechanism for modifying the current thus connected into the circuit according to a particular code.

19; In a telephone-system, the combination of a signaling circuit, a plurality .of tuned ringers connected in said circu1t,'a

' plurality of sourceslof current of difi'erent' frequency adapted to be connected in said circuit, saidsources producing current of a frequencyto which said ringers are respon- 12 5 sive, means for selecting each of said'sources and connecting each in said clrcuit, and

mechanism for breaking the. current from aid sources, 'npinto according to a time of a signaling circuit?? a plurality ofi -f'certaincodei certain frequency calculated to operate. a,

20. In a telephone system, the combination of a sigmiling'circuit including a plurality of tuned ringers, at plurality of sources of current for operating said ringers, each source adapted to produce a current of a plurality of said signals, apparatus to selec- COIIHHUttLt-OI'S differently arranged,

tively connect each of said sources in said circuit, a plurality of connnutators diflerently arranged and means to cause each of "said commutator-s to interrupt the current in said circuit from each of said sources.

21. In atelephone system, the combination of a signaling circuit, a plurality of signals in said circuit, a plurality of sources of signaling current each adapted to produce current of a character l'o which a plurality of said signals are responsive, mechanism to connect any of said sources of current in said circuit, a plurality of commutators having dili'erently arranged contacts and means relay for interrupting said circuit, a plurality ot' commutators difl'erently arranged,

and means to connect each of said commutators in circuit Withsaid relay. I

23. In a telephone system, the combina tion of a ringing circuit, a plurality of tuned ringers connected to said circuit, a plurality of sources of signaling cur 'ent each adapted to supply current to which a pluralitypf said ringers are responsive, apparatus to connect one of said-sources in said circuit, a

rela controllin said circuit a luralit of adapted to be connected in the circuit of said relay, mechanism for selecting and connect- CJI mg said commutator-s in the circuit of said relay and, a common device controlling said a' 'qmratusand aid mechanism. I

24 In a telephone system, the combination of a ringing circuit, a plurality of tuned ringers connected in said circuit, a plurality of sources of frequency current, each adapted to supply currentto operate a plurality of said ringers, a relay for con necting one of said sources in said e1rcu1t,"a'

second relay controlling said circuit and adapted to open and close the same, a plurality of, commutators, each adaptedto be connected in the circuit of the second named relay, a third relay controlling the connec tion of said commutator-s in thecircuit of each the third relay and means including a single key controlling both said first and said third named relays; i

In a telephone system, the combination of a signaling circuit, a plurality of signals connected in said circuit, a plurality of sources of current, each adapted to supply current ot'a character capable of operating' a plurality of said signals, a relay controlling 'the connection of each of said sources to said circuit to the exclusion qfthe other sources, a second relay controlling said signaling circuit andadapted to open and close the same, a plurality of connn'utators dill'erentl arranged for interrupting the circuit olf said second relay, :1 third relay controlling the connection of each of said commutator-s in said'circuit to the exclusion ol the others, and means including a single key controlling said first and third named relays.

26. In a. telephone system, the combination of a signaling ';circuit including a plurality of signals, a plurality of sources of current each adapted to produce current capable of operating a plurality of said signals, means for selecting and connecting said sources in said circuit, a "plurality of devices each adapted to interrupt the current from said sources according to a predetermined code, mechanism for determining which of said devices should act upon the current in the ringing circuit and means including a single keycontrolling both said means.

27. In a telephone system, the combination of a ignaling circuit including a plurality of signals, a plurality of sources of current for simultaneously operating said signals, means for selecting and connecting said sources in aidcircuit, each of said sources'adapted to supplycurrent to operate a plurality of said signals simultaneously,a plurality of commutators for interrupting said current according to a predetermined code, each of-the commutator-s interrupting the current in a manner different i from the 0ther, means to cause said commutators to effect the interruption of said current in a predetermined manner and mechanism including a single key controlling both said current source selecting means and said connnutator selecting means.

28. In a telephone --systei'1'1, the combination of a ringing circuit, a pluralityof ringers in said circuit, each connected between a limb of said circuit and ground, similar to ground, a plurality of sources of ringing current, each adapted to supply current to operate a plurality of said ringers, elec tromagnetic means for determining which of said sources shall be connected in said circuit, a relay for determining to which of rmgersconnected from each of said limbs -n'iining which of 'said devices shall inter the limbs of said circuit -gthe sources 'sha'llbe connected, a plural "fcommutators for interrupting the, flow ofrcurrent in said circuit, saidcoinmiitatom being diiierently arranged to interrupt said: current according to a predetermined code,f, mechanism for determining which of lsaidfcommutators shall interrupt the current in said circuit and means including, a single key controlling said electromagnetic means, said relay and said'me'chanism.

-29. In a telephone system, the combination of a signaling circuit, a plurality of; signals-in said circuit, each connected to alimb of said-circuit, a plurality of sources of signaling current,each adapted to operate aplurality of said signals, devices for interrupting the flow of current'in said circuit according to apredetermined code, said devices being difi'erently arranged and inter rupting said current in a diiierent manner, apparatus for determining which of said sources ofcurrent shall be connected in said circuit, mechanism for determining to which of the limbs of said circuit saidselected source shall be connected, means for deter rupt theflow of current through-said circuit and means including a single key controlling said last named means, said apparatus and said mechanism.

30. In a tel'e hone system, the c'ombination ofa signa ing circuit, a plurality of signals, each connectedto a limb of said circuit, a source of current for supplying current to operate said signals, means, to connect said source in said circuit, mechanism --f or determining'to which of the limbs of. c said circuit said source shall be connected, 4

a plurality of devices for interrupting the flow of current in said' circuit according to apredetermined code, each. of-said (1GV1C6S' being differently (arranged and acting upon the current inqa different manner, apparatus for determining which of said devices shall actlupo'n the current in said circuit and means including; a single key for controllingsaid mechanism and said apparatus.

31. In a telephone system, the, combina tion of'a ringing circuit, a source of ring; ing current and means to connect said source in said circuit, mechanism for determining to which of the limbs of said circuit said source shall be connected, means includinga plurality of. commutators for interrupting the flow of current in said circuit ac,-

" cording to. a predetermined-code, each of said commutators being differently arranged and. influencing the current in the circuit in a di'fl'erentvmanner, apparatus for determining which of-said commutators shall in "fiuence said current and means including a Y single key controlling both said mechanism and said apparatus.

. ing to which limb of said circuit the How of current in said ciitcuitacco .and said keys.

32. Iii a telephone system, the combination of a signaling circuit, a plurality of signals, each connected to a limb of said ="circuit, a plurality of sources of signaling to a predetermined code, each of said co nimitators being differently arranged and cal- V culated to difierently affect. the flow of current=in said circuit, a third relay determin-.

ing which of said commutat-ors shall' afiect the'flow of current in' said circuit, a plurality of keys,onecontrollingeach of said relays, a plurality of'keys, one controlling each pairof-said relaysanda key control- -ling all-three of said relays, a source of current andsuitable conductors connecting said keys and said relays; r

33. In a telephonefsystem,:the combi tion of a' signaling circuit, a plurality. of signals, each connected to a limb of said circuit, a plurality of sources of signaling current, a relay fordetermining and controlhug the -connec t1onof each of said sources in said circuit,a-second relay for determin sourceshall be connected, mea is f plurality of commutators for int to a predetermined code, each ofj -sa-i'cl mutat'ors being difi'erently arranged and culated 'todiiferent'ly affect the flow-of:

rentin said circuit,- a third relay'determiiiing which of said 'commutators shall affect the fioyv. of current in said circuit, a key coniI-IOlllllg' said first named relay, a second key controlling said first and second named relaysiand a third relay controlling allof-said:

relays, a source of current and icircu-itlconductors associating 34, In a telephone system, the combinacircuit, 'aiplur'ality of sources of signaling current, a relay for determining and controlsaidsour'ce, said relays 7 tion of a signaling circuit, a plurality of "signals, each connected to a-limbof said i ling the connection 'of each of said sources. in said circu t, a second relay for determin ing to which limbxofsaid circuit a selected source sh'all'be connected, meansincluding a plurality of commutators for interrupting the flow of current in said circuitaccording ,to a predetermined code, each-of sa1d commutators being differently arranged and calrent in said circuit, a-third relay determining which of said coinmiitators shall affect the flow of current in said circ'uit,'a setof keys, one, controlling-teach of said relay, a.

' cu'lated to difi'erently affect the flow of curi BEST AVAILABLE o'oPY- 4,298,589 j to which said signal is connected, a sig' nal-ing key normally having no control over" the connection of saidvsource to said telephone lines, means controlled by the answering switch for assigning to said key the connection of said source to said line, and means controlled byfthe calling switch for removing from said key control of the connection ofsaid source to said line. Y

36. In a telephone system, the combination of a pin 'ality of telephone lines, a subscr'ibers signal connected to-oneof said lines, a main station, a cord circuit at the main station for connecting lines together, an an swering plug and jackswitch for connecting the cord to a calling line, a calling plug and jack switch for connecting the cord to it called line, a source of current for supplying current to operatesaidsignal, eoiuluctors for-connecting said source to terminals of the calling plug, aringing-key llOlllltllly exercising no control over said conductors, means operated when the answering plug is inserted into the jack of the calling line tor assigning control over said conductors to said key, and mechanism operated when the calling plug is inserted intofthe ack of the called line for discharging said key from control over said conductors.

37. In a telephone system, the combination of a main statiointelephone lines lcading to the main station, a signal on one of said lines, link conductors at the main station for connectingsaid lines together, an answering switch and a calling switch for connecting said link:=condilctors to telephone lines, a source of signaling current adapted to supply current to oper 'ite said signal, conductors for connectingsaijdsource to the terminals of the calling switchfa relay controlling said conductors. a'signaling key normally having no control over said relay, means controlled M t answering switch for placing said relay under the control of said key and mechanism controlled by the calling switch for discharging said relay from the control of said key.

38. In a telephone system, the combine tion of a plurality of telephone lines, a substation signal on one of said lines, a main station,l' a cord circuit at the main station, an answering switch for connecting the cord to one of said lines, a calling switch for connecting the cord-to another of said lines,

a source of signaling current adapted to supply current to operate the signal, conductors for connecting said source to a terminal of the calling switch, a relay controlling said conductors, a signaling key, a normally open circuit including said relay and said key, means controlled by the answering switch for closing said circuit and placing said relay under the control of said key, a second circuit for saidrelay and means controlled by the callingswitch [or opening the first named circuit and discharging the control of the relay from the key and-closing the second circuit. for said relay independently o l the. lirst circuit.

3 In a telephone system. the combination of a pair of telephone lines, a signal on one of said lines, link conductors for connecting the lines together, an answering switch for connecting' the link conductors -to one of said lines, a calling switch [or connecting the link conductors to the other or said llllt.$.. a signaling circuitincluding 'one ot'said lines, said signal and a source oisignaling current, a key for controlling said circuit normally having no control thereovei'. means operated whilethe answering switch alone is operated for placing the ringing circuit .under the control of said key and means actuated while both of said ans\ \'cringswitch and a calling switch each adaptcd when operated to connect the linkconductors to one of ou lines, a ringing circuit including one of said lines, a signal I on the line inc-the ringing circuit. a source of signal operating current adapted to be connected in said ringing circuit, a relay controlling normally open contacts in said ringing circuit, means for energizing said relay when theanswering switch is operated and means fordeiinergizing said relay when the calling switch is operated. 41. In a telephone system, the coinbination of-a calling line and a called line. a

signal on the called line, a cord circuit for connecting the lines together, an answering switch for connectingtlie cord to the alling line, a calling switch for coniiect'ii-ig the cord to the called line, a ringing circuit including a portionof the cord circuit and the called line, a source of signal operating current adapted to be connected in saidcircuit, a relay controlling the connection of sai'dsource in said circuit, a circuit for said relay, a second relay controlling's'aid c v swerin g' and calling connective switches,'a'

trolled by the answeringswitcht j 42,- In a telephone syste'm,';'a calling telecuit. and. a circuit for thes'econd" relay conphone" line, 'a called telephone line, .a plural1ty' of connective circuits having an-- relay operated'when connection made means of the answering sw tch of a oonnecti-Veeireuiflwith a calling tele hone-line,

a sele 'ctilve 'key common to aplurality' ,of

connectivecireuits and adapted to be associated. with the' particular connective "cir sta'tions, a connecti'ye "circuitadapted to connect a calling line to saidealled party line, other [connective circuits which likewise are adapted to connect calling and called telephone lines, 'a selective relay in each of all saidcord circuits and adapted when actuated to select aparticular character of ringing current, a control relay operated when ,conneoti'on is made between the connective-circuit anda calling line, said control relay causing the connectlon of a selective key to said connect ve c1rcu1t, circuit conductors permitting saidselective" keyto'then operate sziidQselectiveielay, av

nectiye circuit to said party line, a ringing .relay, said ringing. relay, adapted to apply said selected ringing current to the called p'arty line, electromagnetic means operated when said calling switch is connected to said called line, said electromagnetic means being-adapted to slowly release said control relay, circuit connections established during the'int'erval while said control relay is being calling switch adapted to, connect said conrestored to norinallto cause "said. r1n'ging"re- --1ay to operate, and a circuit independent .of

said .control relay established upon this: Op", eration 'to maintain said ringing relay until the response of the called subscriber, and.

electromagnetic means operative upon said response to restore said ringing relay to.

normal,

I have hereunto afiix ed 'my. signature this 7th day of June, 1915. l V v FRANK M. S'LQUGH,

I 13.1111 a telephone system, the combination'of wig-mun circuit, a pluralityv v c I of sources ofcuireht,each-adapted toheconnected infsaid circuit, one normally connected in'said circuit, a relay controlling 1theconnection of each of'gaid sources in said circuit, another sourceof signaling-current adapted to be connected in said circuit, all of said relays. jointlywcontrolling "the fconnectionof said last named "sourcein said circuit and means controlling said relays. i i v L 14. In a telephone system, the combination of a signaling circuit, a plurality] a ofsources of current, each adapted'to' be connected in said circuit one normally connected in said circuitifarelayrontrollingthe connection of each of said sources 7 in said circuit, a key controlling each ofisaid relays athirdsource of signaling j V I current adapted to be connected in said circuit, means including all of said relays controlling the connection of athird source in said circuit and another ringing key controlling allof said'relaysi I f v g 17. In a telephone system,the combination of a signaling" circuit including a plurality of signals, a plurality 'icfsource's of signaling current for selectively operating said' signals, mechanism for selectingand-connecting said sour es in'said A v circuit, a plurality of devices for modifying theeffect ofthe current from said -'sources'onfsaidsignals and means for selectively causing said: devices, each indeendently of the otherto modify the eifectfof current} from eachcsou'rce upon said l c. c c y 18. In a tel phone system,the combinatio'nof,asignaling circuit'includinga I vplurality of signals, each signal constructedftq' respond'to a particular one ofa Y Q- :K plurality of currents-of diiferentgcharacter,.means forproducinga number of, currentsbf differentcharacter,'means for determining which-character of current shall be connected in saidcircuitand' mechanism for modifyingthe current thus" connected into the circuit'acc'ording to a particular code; 1 7 p I 19.- In a telephone'system, the combination of a signaling circuit, a "plurality I i of tuned ringers connected said-circnit, a plurality of, sources of current of difi'erent frequency adaptedjto be connected said circuit, said sources producin I current of a frequencyto which. said ringers are'res'pon'siveg' means foriselec'ting 1 each of said sources and connecting eachin said circuit,- and. mechanism for break- .ing the current from said sources uplintojperiods according to afcertain code; i

H F20. In a telephone system,"the combinationofa signaling?circuitincluding a,

plurality "of t'unedrin'gers, a 'pluralityof sources of "current for 'operating said.

ringers, each source adapte'dgtoproducea current of a certain frequency calculated n to operate a plurality of said signals,"apparatus to selectively connect each of said sourcesin said circuit,a plurality otcommutatorsdifferently arranged'and meansto cause each of said commutators to interrupt the currentsin said circuit from each'of said sources. I; c

, 7 21; In a telephone system, the combination of a signaling circuit, a plurality of signal$-in said circuit, a plurality ofsourccsoffsignalingicurrcnt each adapted to produce current of acharacter to whicha plurality of: said signals are resp'onc sive, mechanism to connect any o-f'saidsources'of current in said circuitya pin: 7

a rality of commutators having differently arranged contacts'land imeans for causi ingeither ofsaid commutators to interrupt the current in said'vcircuit from either of said sources; 1' i Y i I i 7 v 41. In a telephone system, thdoombination of a calling line and a called line,

- a signal on the'calle'd line, a cordfcircuit .for connecting the lines together; an g answerin'gswitchfor connecting-Ethe cord, to the calling line,a,ca1ling switch for connecting the cord to the called line; a 1 ringing circuitincludingIa portion of the cord'circuit and the called line-,xa source ofsignal operating current adapted to be connected in said circuit fla' relay controlling the connection of said source in said; circuit, a circuit for said relaygiasecond relayfcontrolling said circuit and-a circuit Q for the secondrelay controlled bythe answering SWitQ 3 I p i u [Ozfioz'al Gazette Marchf27, 1923;] 1 

